Extrusion press device and extrusion press method

ABSTRACT

An extrusion press device according to the present invention includes: an extrusion unit that includes a container configured to store an extrusion material and an end platen configured to support a die-from which the extrusion material is extruded; and a control unit configured to control operation of the extrusion unit, including container sealing force that presses the container against the die. The control unit performs control to apply complementary pressure corresponding to reduced container sealing force that is increased along with progression of extrusion, to the container in a direction of the extrusion during a period from start to completion of the extrusion.

TECHNICAL FIELD

The present invention relates to an extrusion press device and anextrusion press method used for extrusion molding of a metal materialsuch as an aluminum alloy.

BACKGROUND ART

In an extrusion press device that extrudes and molds an extrusionmaterial called a billet that is made of a metal material such asaluminum and an alloy material thereof has an extrusion stem attached,through a main crosshead, at a front end part of a main ram of a maincylinder that is driven and advanced by hydraulic pressure. Extrusionmolding by the extrusion press device includes an upset process and anextrusion process. In the upset process, in a state where a container ispressed against a die disposed on an end platen side, by a containercylinder and the like, the extrusion stem is advanced to cause the dieto press the extrusion material stored in the container. In theextrusion process, the main ram is further advanced to cause the die topress the extrusion material by the extrusion stem, and a predeterminedproduct is extruded and molded from the die.

In such extrusion molding by the extrusion press device, force pressingthe container against the die disposed on the end platen side, by thecontainer cylinder and the like is referred to as container sealingforce. The container sealing force is force applied to the container bya hydraulic cylinder such as the container cylinder during the extrusionprocess in order to prevent a “bursting phenomenon” when the extrusionmaterial stored in the container is pressed by the extrusion stem. The“bursting phenomenon” is a phenomenon in which the extrusion material isextruded from a gap between an end surface of the die and a front endsurface of the container.

For example, Patent Literature 1 discloses an equal-pressure extrusioncontrol method that controls the container sealing force acting on thedie during the extrusion process to be constant during a period fromstart to completion of the extrusion.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2013-035036 A

SUMMARY OF INVENTION Technical Problem

According to the equal-pressure extrusion control method disclosed inPatent Literature 1, it is possible to prevent the “bursting phenomenon”that often occurs in a second half of the extrusion process throughprevention of reduction of the container sealing force along withprogression of the extrusion process.

The equal-pressure extrusion control method disclosed in PatentLiterature 1, however, decreases the container sealing force acting onthe die by pressing a container holder in a direction opposite to theextrusion during a period from the start to the middle of the extrusion,namely, in a first half of the extrusion process. The equal-pressurecontrol method disclosed in Patent Literature 1 controls the containersealing force acting on the die during the extrusion process to beconstant during the period from the start to the end of the extrusionthrough the decrease of the container sealing force.

As described above, in the Patent Literature 1, the die is pressed inthe direction opposite to the extrusion in the first half of theextrusion process. Therefore, reaction force of extruding force actingbetween the end platen and a main cylinder housing coupled by, forexample, a tie rod is continuously reduced from the start of theextrusion. When the reaction force of the extruding force iscontinuously reduced, a deformation amount of the end platen receivingthe reaction force of the extruding force through the die is reduced,and the deformation amount influences a deformation amount of the die.The deformation of the end platen is deflection mainly caused by curveddeformation, and the deformation of the die is deflection caused bycompression and curvature in a longitudinal direction. These deflectionadversely affects accuracy of an extruded product.

The present invention is made in consideration of the above-describedissues, and an object of the present invention is to provide anextrusion press device and an extrusion press method that make itpossible to suppress deflection of an end platen, a die, and the likewhile preventing a “bursting phenomenon”.

Solution to Problem

An extrusion press device according to the present invention includes:an extrusion unit including a container configured to store an extrusionmaterial, and an end platen configured to support a die from which theextrusion material is extruded; and a control unit configured to controloperation of the extrusion unit. A target of the control by the controlunit includes container sealing force that presses the container againstthe die.

The control unit according to the present invention performs control toapply complementary pressure corresponding to reduced container sealingforce that is increased along with progression of extrusion, to thecontainer in a direction of the extrusion during a period from start tocompletion of the extrusion.

The control unit according to the present invention preferably controlsapplication of the complementary pressure to maintain referencecontainer sealing force that is the container sealing force at the startof the extrusion, during the period from the start to the completion ofthe extrusion.

The control unit according to the present invention preferably handlescontainer sealing force calculated at the start of the extrusion, as thereference container sealing force.

The control unit according to the present invention preferablycalculates the reduced container sealing force as a difference betweencontainer sealing force during the extrusion and the reference containersealing force.

The control unit according to the present invention preferably performscontrol to apply, as the complementary pressure, force of 20% or moreand 30% or less of maximum actual extruding force at the start of theextrusion, to the container.

The extrusion unit according to the present invention preferablyincludes a container cylinder that advances the container to approachthe end platen or retreats the container to separate from the endplaten.

The container cylinder preferably includes a first oil chamber and asecond oil chamber that are arranged in a longitudinal direction X alongthe extrusion direction, and each of the first oil chamber and thesecond oil chamber preferably includes two divided oil chambers dividedin the longitudinal direction X.

The control unit according to the present invention preferably includesan equal-pressure extrusion control hydraulic circuit that supplieshydraulic oil to one or both of the first oil chamber and the second oilchamber of the container cylinder when the container is advanced by thecontainer cylinder. The equal-pressure extrusion control hydrauliccircuit is independent of a hydraulic circuit to extrude the extrusionmaterial.

The present invention provides an extrusion press method of extruding anextrusion material from a die while pressing a container against the dieto apply container sealing force, the extrusion material being extrudedfrom the die and being stored in the container.

In the extrusion press method according to the present invention, adifference between reference container sealing force and in-extrusioncontainer sealing force is handled as reduced container sealing force.At this time, the reference container sealing force is container sealingforce at start of extrusion in the extrusion press method that extrudesthe extrusion material from the die while pressing the container againstthe die to apply the container sealing force, the extrusion materialbeing extruded from the die and being stored in the container. Further,the in-extrusion container sealing force is the container sealing forceduring the extrusion.

In the extrusion press method according to the present invention,complementary pressure corresponding to the reduced container sealingforce is applied to the container in a direction of the extrusion duringa period from the start to completion of the extrusion.

In the extrusion press method according to the present invention, thecomplementary pressure is preferably applied to maintain the referencecontainer sealing force at the start of the extrusion during the periodfrom the start to the completion of the extrusion.

In the extrusion press method according to the present invention, thereference container sealing force and the in-extrusion container sealingforce are preferably based on information detected at and after thestart of the extrusion. Further, the reduced container sealing force andthe complementary pressure are calculated during the extrusion, based onthe detected reference container sealing force and the detectedin-extrusion container sealing force.

Advantageous Effects of Invention

According to the present invention, the complementary pressurecorresponding to the reduced container sealing force that is increasedalong with progression of the extrusion, is applied to the container inthe extrusion direction during the period from the start to thecompletion of the extrusion. As a result, the extruding forcepropagating to the end platen through the die is maintained to beconstant during the period from the start to the completion of theextrusion. Accordingly, the amount of deflection occurred on the endplaten and the die caused by the extruding force is maintained in thestate at the start of the extrusion, until the completion of theextrusion.

In addition, according to the present invention, control is performed toapply the complementary pressure corresponding to the container sealingforce that is reduced along with progression of the extrusion, to thecontainer in the extrusion direction during the period from the start tothe completion of the extrusion. Applying the complementary pressuremakes it possible to secure the container sealing force sufficient toprevent the “bursting phenomenon” during the period from the start tothe completion of the extrusion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic plan view of an extrusion press device accordingto a first embodiment.

FIG. 2 is a schematic front view of a main cylinder housing of theextrusion press device according to the first embodiment.

FIGS. 3A and 3B each are a schematic cross-sectional view of a containercylinder of the extrusion press device according to the firstembodiment.

FIG. 4A is a partial enlarged view of FIG. 1 and illustrates forcegenerated in elements of the extrusion press device, FIG. 4B is a graphillustrating variation of extruding force F and container sealing forcef during an extrusion process, and FIG. 4C is a graph illustratingequal-pressure extrusion control according to the first embodiment.

FIG. 5 is a schematic hydraulic circuit diagram to perform anequal-pressure extrusion control method by the extrusion press deviceaccording to the first embodiment.

FIG. 6 is a flowchart illustrating a procedure to calculate variouskinds of parameters according to the first embodiment.

FIG. 7A is a flowchart illustrating a procedure to set referencecontainer sealing force, and FIG. 7B is a flowchart illustrating aprocedure to calculate reduced container sealing force.

FIG. 8 is a schematic hydraulic circuit diagram to performmain-crosshead retreat control method by an extrusion press deviceaccording to a second embodiment.

DESCRIPTION OF EMBODIMENTS

An extrusion press device and an extrusion press method according topreferred embodiments of the present invention are described in detailbelow with reference to accompanying drawings. Note that the followingembodiments do not limit the invention according to the scope ofappended claims, and of combinations of features described in theembodiments are not necessarily essential for means for solving theproblem of the invention.

First Embodiment

First, a main configuration of an extrusion press device 1 according toa first embodiment is described with reference to FIG. 1 and FIG. 2.

[Extrusion Unit 3 in Extrusion Press Device 1]

The extrusion press device 1 according to the first embodiment includes,as an extrusion unit 3, an end platen 10, a main cylinder housing 12,and a main cylinder 12A.

The end platen 10 supports a die 16 by a surface on a side facing themain cylinder housing 12. The main cylinder housing 12 is disposed so asto face the end platen 10, and is coupled with the end platen 10 by aplurality of tie rods 14. The main cylinder 12A is disposed at asubstantially center of the main cylinder housing 12.

The extrusion press device 1 further includes, as the extrusion unit 3,a main crosshead 22 and a main ram 12B.

The main crosshead 22 is disposed between the end platen 10 and the maincylinder housing 12, and an extrusion stem 24 is disposed so as toprotrude from a front end surface of the main crosshead 22. One end sideof the main ram 12B is fixed to a rear end surface of the main crosshead22, and the other end side is stored in the main cylinder 12A. The mainram 12B advances the main crosshead 22 to approach the end platen 10.

The extrusion press device 1 further includes, as the extrusion unit 3,a plurality of side cylinders 26, a container 18, and a plurality ofcontainer cylinders 28.

As illustrated in FIG. 2, the side cylinders 26 are disposed around themain cylinder 12A, and advance the main crosshead 22 to approach the endplaten 10 or retreat the main crosshead 22 to separate from the endplaten 10.

The container 18 is disposed between the end platen 10 and the maincrosshead 22, and stores an extrusion material EM.

The container cylinders 28 advance the container 18 fixed to a containerholder 19, to approach the end platen 10, or retreat the container 18 toseparate from the end platen 10.

Note that, in the extrusion press device 1, a side on which the endplaten 10 is disposed is defined as front, and a side on which the maincylinder housing 12 is disposed is defined as back. In FIG. 1, FIG. 3A,FIG. 3B, FIG. 5, and FIG. 8, front is denoted by (F), and back isdenoted by (B). Further, the terms front and back include relativemeanings. For example, it can be said that the main crosshead 22 isdisposed on the back side of the container holder 19.

Further, in the extrusion press device 1, a longitudinal direction X isdefined by arrows illustrated in FIG. 1, FIG. 3A, FIG. 3B, and FIG. 8.Further, an extrusion direction is defined by a direction illustrated bya left arrow out of the arrows representing the longitudinal directionX.

[Container Cylinder 28]

The container cylinders 28 include characteristic elements in theextrusion press device 1. More specifically, the container cylinders 28are disposed in the main cylinder housing 12, and advance the container18 from the main cylinder housing 12 side to press the container 18against the die 16 disposed on the end platen 10 during an extrusionprocess.

Further, each of the container cylinders 28 has a so-called tandemstructure. More specifically, as illustrated in FIG. 3A and FIG. 3B,each of the container cylinders 28 includes a plurality of oil chambersin the longitudinal direction X of a cylinder rod 28A. Each of thecontainer cylinders 28 is characterized in that the cylinder rod 28Acommunicating with the oil chambers is provided with pistons slidable inthe longitudinal direction X in the respective oil chambers, and twodivided oil chambers divided in the longitudinal direction X by thepiston are formed in each of the oil chambers. A specific configurationof one container cylinder 28 is described with reference to FIG. 3A andFIG. 3B. FIG. 3A illustrates a state where the cylinder rod 28A of thecontainer cylinder 28 is retreated up to a retreat limit position, andFIG. 3B illustrates a state where the cylinder rod 28A of the containercylinder 28 is located at an intermediate position.

In the container cylinder 28, a first oil chamber 51 and a second oilchamber 61 are arranged in the longitudinal direction X in order fromthe container 18 (front F) side. The first oil chamber 51 and the secondoil chamber 61 are partitioned by a coupling portion 71. The cylinderrod 28A communicating with both of the first oil chamber 51 and thesecond oil chamber 61 has a configuration in which a first rod 52communicating with the first oil chamber 51 on the front side (F) and asecond rod 62 communicating with the second oil chamber 61 on the backside (B) are coupled by a screwing structure or the like on the firstoil chamber 51 side. The first oil chamber 51 on the front side (F) isprovided in a first cylinder body 53 through which the first rod 52penetrates. The second oil chamber 61 on the back side (B) is providedin a second cylinder body 63. Further, the first cylinder body 53 andthe second cylinder body 63 are fixed to the coupling portion 71 suchthat an opening on the back side (B) of the first cylinder body 53 andan opening on the front side (F) of the second cylinder body 63 faceeach other. The second rod 62 communicating with the second oil chamber61 penetrates through the coupling portion 71. As a result, the firstoil chamber 51 and the second oil chamber 61 are provided as independentoil chambers.

On the other hand, a first piston 54 that divides the first oil chamber51 into two sections in the longitudinal direction X is provided at acoupling part between the first rod 52 and the second rod 62 on thefirst oil chamber 51 side. Further, a second piston 64 that divides thesecond oil chamber 61 into two sections in the longitudinal direction Xis provided at a back end of the second rod 62. The first piston 54 andthe second piston 64 are attached to respective corresponding portionsby a screwing structure or the like.

A seal fixing member 55 that fixes a sealing member and the like for thefirst rod 52 is attached to the front side (F) of the first cylinderbody 53. Further, a closing member 65 that closes the opening on theback side (B) of the second cylinder body 63 and fixes a sealing memberis attached to the opening.

As illustrated in FIG. 3B, in the container cylinder 28 having theabove-described configuration, the first oil chamber 51 is divided intoand referred to as a divided oil chamber 56A and a divided oil chamber56B, and the second oil chamber 61 is divided into and referred to as adivided oil chamber 66A and a divided oil chamber 66B.

The divided oil chamber 56A occupies a front section of the two sectionsdivided in the longitudinal direction X from the first oil chamber 51 bythe first piston 54, namely, the front side (F) of the first piston 54.The divided oil chamber 56B occupies a back section of the first oilchamber 51, namely, a section between the first piston 54 and thecoupling portion 71. Further, the divided oil chamber 66A occupies afront section of the two sections divided in the longitudinal directionX from the second oil chamber 61 by the second piston 64, namely, asection between the coupling portion 71 and the second piston 64. Thedivided oil chamber 66B occupies a back section of the second oilchamber 61, namely, a section between the second piston 64 and theclosing member 65.

Hydraulic pipes P1, P2, P3, and P4 are connected to the divided sectionsof the first oil chamber 51 divided in the longitudinal direction X bythe first piston 54 and the divided sections of the second oil chamber61 divided in the longitudinal direction X by the second piston 64.

To advance and press the container 18, hydraulic oil is supplied to atleast one of the divided oil chamber 56B and the divided oil chamber 66Bthrough at least one of the hydraulic pipe P2 and the hydraulic pipe P4.To obtain large output, the hydraulic oil is supplied to both of thehydraulic pipe P2 and the hydraulic pipe P4. Further, to retreat thecontainer 18, the hydraulic oil is supplied to at least one of thedivided oil chamber 56A and the divided oil chamber 66A through at leastone of the hydraulic pipe P1 and the hydraulic pipe P3. Likewise, toobtain large output, the hydraulic oil is supplied to both of thehydraulic pipe P1 and the hydraulic pipe P3.

Note that FIGS. 3A and 3B illustrate the example of the specificconfiguration of the container cylinder 28, and the configuration of thecontainer cylinder 28 according to the present invention is not limitedto the configuration illustrated in FIG. 3A and FIG. 3B. For example, asillustrated in FIG. 5, the present invention can adopt a single cylinderform in which one oil chamber is divided by one piston. Further, forsimplification of the drawing, illustration of the sealing member, thescrewing structure, and the fixing member (such as bolt) is omitted inFIG. 3A and FIG. 3B.

[Container Sealing Force]

Next, the container sealing force is described with reference to FIG. 4Ato FIG. 4C.

As illustrated in FIG. 4A, container sealing force f that presses thecontainer 18 against the die 16 is generated on a contact surface of thedie 16 and the container 18.

During the extrusion process, when the extrusion material EM stored inthe container 18 is pressed against the die 16 by the extrusion stem 24,the extrusion material EM is plastically deformed in a circumferentialdirection inside the container 18 by extruding force F applied to theextrusion material EM. An outer peripheral surface of the extrusionmaterial EM comes into surface contact with an inner peripheral surfaceof the container 18 that stores the extrusion material EM. Therefore,frictional force Fb occurs between the outer peripheral surface of theextrusion material EM and the inner peripheral surface of the container18 during the extrusion process. Accordingly, the extruding force F thatis to be applied to the extrusion material EM by the extrusion stem 24in an advancing direction approaching the end platen 10 is representedby a sum of necessary extrusion force Fa acting on the die 16 throughthe extrusion material EM and the frictional force Fb, namely, F=Fa+Fb.

The necessary extrusion force Fa is extrusion resistance force of thedie 16 when the extrusion material EM is extruded and molded from thedie 16 in a state with no frictional force Fb. Assuming that temperatureof the extrusion material EM is not varied during the extrusion process,the necessary extrusion force Fa is substantially uniform during aperiod from the start to the completion of the extrusion.

On the other hand, the frictional force Fb is the largest at the startof the extrusion, and the frictional force at the start of the extrusionis referred to as the maximum frictional force Fbmax. This is because acontact area between the extrusion material EM and the container 18 isthe largest at the start of the extrusion. The contact area hasproportional relationship with a dimension in the longitudinal directionX of the extrusion material EM located inside the container 18, namely,an extrusion material length L.

The frictional force Fb is continuously reduced in proportion toreduction of the extrusion material length L along with progression ofthe extrusion process. Further, when the extrusion material length Lbecomes the minimum extrusion material length Lmin at the completion ofthe extrusion, the frictional force Fb becomes the minimum frictionalforce Fbmin.

Accordingly, as illustrated in FIG. 4B, the extruding force F (Fa Fbmax)at the start of the extrusion is reduced to Fa Fbmin at the completionof the extrusion. A lateral axis of FIG. 4B indicates the extrusionmaterial length L of the extrusion material EM, and an origincorresponds to the maximum extrusion material length Lmax. The originindicates start of the extrusion, and the extrusion material length L atthis time is the maximum extrusion material length Lmax. Likewise, avertical axis indicates the extruding force F.

In addition, as illustrated in FIG. 4A, reaction force Fb′ of thefrictional force Fb between the extrusion material EM and the container18 acts on the container 18 in a direction in which the container 18 ispressed against the die 16, namely, in the same direction as thecontainer sealing force f. The reaction force Fb′ is typically about 30%of the maximum actual extruding force F, and at least the maximumreaction force Fbmax of the maximum frictional force Fbmax at the startof the extrusion is force sufficient as the container sealing force fpreventing the “bursting phenomenon”. Accordingly, when the force lowerthan or equal to 30% or preferably higher than or equal to 20% of themaximum actual extruding force is applied as complementary pressure Pato the container 18, it is possible to prevent the “burstingphenomenon”.

[Control Unit 5 of Extrusion Press Device 1]

Next, a hydraulic circuit to operate the extrusion press device 1 isdescribed with reference to FIG. 5.

The extrusion press device 1 is provided with the hydraulic circuitincluding an equal-pressure extrusion control hydraulic circuit 84 thatincludes pressure detection means 81, an equal-pressure extrusioncontrol hydraulic-oil supply source 82, and equal-pressure extrusioncontrol pressure control means 83. The extrusion press device 1 isprovided with a controller 85 controlling operation of theequal-pressure extrusion control hydraulic circuit 84 that includes thepressure detection means 81, the equal-pressure extrusion controlhydraulic-oil supply source 82, and the equal-pressure extrusion controlpressure control means 83.

The equal-pressure extrusion control hydraulic circuit 84 that includesthe pressure detection means 81, the equal-pressure extrusion controlhydraulic-oil supply source 82, and the equal-pressure extrusion controlpressure control means 83, and the controller 85 configure a controlunit 5.

In the following, the equal-pressure extrusion control hydraulic-oilsupply source 82, and the equal-pressure extrusion control pressurecontrol means 83, and the equal-pressure extrusion control hydrauliccircuit 84 are respectively abbreviated to the hydraulic-oil supplysource 82, the pressure control means 83, and the control hydrauliccircuit 84.

The pressure detection means 81 detects pressure of the hydraulic oilinside the main cylinder 12A when the main crosshead 22 is advanced. Thepressure detection means 81 further detects pressure of the hydraulicoil supplied to the main cylinder 12A. The pressure detection means 81includes a pressure sensor such as a pressure pickup.

To advance the container 18, the hydraulic-oil supply source 82 suppliesthe hydraulic oil to one or both of the divided oil chamber 56B of thefirst oil chamber 51 and the divided oil chamber 66B of the second oilchamber 61 in each of the container cylinders 28. To retreat thecontainer 18, the hydraulic-oil supply source 82 supplies the hydraulicoil to one or both of the divided oil chamber 56A of the first oilchamber 51 and the divided oil chamber 66A of the second oil chamber 61in each of the container cylinders 28.

In the case of the container cylinders 28 based on the single cylinderillustrated in FIG. 5, when the hydraulic oil is supplied to the oilchamber 56A and the oil chamber 56B, a differential pressure circuit isconfigured. This makes it possible to increase the advance speed of therod.

The hydraulic circuit having the above-described configuration is ahydraulic circuit that is dedicated to advance/retreat the container 18and is independent of the hydraulic circuit from a main hydraulic-oilsupply source. The hydraulic-oil supply source 82, however, is not usedonly for equal-pressure extrusion control during the extrusion process,and can be driven together with the main hydraulic-oil supply source ata time other than the extrusion process. In FIG. 3A and FIG. 3B, tosimplify the hydraulic circuit, illustration of the main hydraulic-oilsupply source and the hydraulic circuit from this supply source isomitted. The main hydraulic-oil supply source includes, for example, oneor more hydraulic pumps. Note that, in the schematic hydraulic circuitdiagram of FIG. 5, a symbol of a variable discharge hydraulic pump isillustrated as the hydraulic pump of the hydraulic-oil supply source 82;however, the hydraulic pump of the hydraulic-oil supply source 82 may bea hydraulic pump, the discharge amount of which is controlled throughrotational speed control of a driving motor.

When the extrusion stem 24 is advanced to extrude the extrusion materialEM stored in the container 18 from the die 16 in the extrusion process,the hydraulic oil is supplied from the unillustrated main hydraulic-oilsupply source to the main cylinder 12A and the side cylinders 26. Thehydraulic oil is supplied at pressure and the discharge amount necessaryto advance the extrusion stem 24 and the main crosshead 22 with thedesired extruding force F at the desired extrusion speed.

Note that FIG. 5 is the schematic hydraulic circuit diagram to performthe equal-pressure extrusion control method by the extrusion pressdevice 1 according to the first embodiment. Therefore, only main valvesand pressure control devices necessary for description have been denotedby the reference numerals and described. Accordingly, all of thehydraulic devices necessary for the actual hydraulic circuit are notillustrated, and valves not denoted by the reference numerals among theillustrated valves are only illustrated as “OPENED” or “CLOSED” in FIG.5.

At the start of the extrusion, a container sealing process in which thecontainer 18 is advanced by t container cylinders 28 and is pressedagainst the die 16 has been already completed. Accordingly, the dividedoil chamber 56B and the divided oil chamber 66B of each of the containercylinders 28 are filled with the hydraulic oil at pressure equivalent tothe initial container sealing force, and the container sealing force fis controllable by the control hydraulic circuit 84.

The hydraulic circuit according to the present embodiment in this statecan perform the equal-pressure extrusion control method while variationof the extruding force F is suppressed because the hydraulic circuitincludes the control hydraulic circuit 84 that includes thehydraulic-oil supply source 82 and the pressure control means 83.

The control procedure is described below with reference to FIG. 6, FIG.7A and FIG. 7B as well. The procedure described below is divided into aprocedure to calculate the complementary pressure Pa in theequal-pressure control and an equal-pressure extrusion control procedureto control operation of the container cylinders 28 by applying thecalculated complementary pressure Pa.

[Calculation of Complementary Pressure Pa in Equal-Pressure Control]

As illustrated in FIG. 6, the control procedure described here includesa reference container sealing force setting step (S101 in FIG. 6), areduced container sealing force calculation step (S103 in FIG. 6), and acomplementary pressure calculation step (S105 in FIG. 6). The controlprocedure is a procedure to calculate the complementary pressure Pa thatis applied to prevent the bursting phenomenon during the extrusionprocess. The procedure is executed by the controller 85.

[Reference Container Sealing Force Setting Step]

A specific exemplary procedure of the reference container sealing forcesetting step (S101 in FIG. 6) is described with reference to FIG. 7A aswell.

First, at the start of the extrusion process, the pressure detectionmeans 81 detects start pressure Ps of the hydraulic oil (S201).

The controller 85 acquires the start pressure Ps detected by thepressure detection means 81, and calculates start actual extruding forceFs based on the start pressure (S203). Further, the controller 85 alsocalculates force acting on the die 16 through the container 18 by thestart actual extruding force Fs, namely, the maximum frictional forceFbmax (=maximum reaction force Fb′max) between the extrusion material EMand the container 18 by the extruding force F (S205). The controller 85sets the maximum reaction force Fb′max as the reference containersealing force fs (S207).

[Reduced Container Sealing Force Calculation Step]

Next, the reduced container sealing force calculation step (S103 in FIG.6) is described with reference to FIG. 7B.

The pressure detection means 81 detects in-extrusion pressure Pex thatis pressure of the hydraulic oil while the extrusion process progresses,and the controller 85 acquires the detected in-extrusion pressure Pex(S301). The controller 85 calculates in-extrusion actual extruding forceFex based on the acquired in-extrusion pressure Pex, and the frictionalforce Fb (=reaction force Fb′) during the extrusion by the in-extrusionactual extruding force Fex (S303 and S305).

Further, the controller 85 sets the calculated reaction force Fb′ asin-extrusion container sealing force fex (S307), and calculates reducedcontainer sealing force fd that is a difference between the in-extrusioncontainer sealing force fex and the reference container sealing force fs(S309).

Referring back to FIG. 4C, the reduced container sealing force fd isdescribed.

The reaction force Fb′ at the time when the extrusion material length Lis L1 is regarded as the in-extrusion container sealing force fex(fex=Fb′). The controller 85 calculates the reduced container sealingforce fd that is a difference between the in-extrusion container sealingforce fex and the reference container sealing force fs (fd=fs−fex). Thereduced container sealing force fd is substantially equal to thereduction amount of the frictional force Fb or the reduction amount ofthe reaction force Fb′ (Fbmax−Fb or Fb′max−Fb′) reduced during theextrusion process, and is increased along with progression of theextrusion.

[Complementary Pressure Calculation Step]

Next, the controller 85 calculates force that is substantially equal tothe reduced container sealing force fd calculated in the reducedcontainer sealing force calculation step in the extrusion direction, asthe complementary pressure Pa of the container sealing force (S105 inFIG. 6). The complementary pressure Pa is supply pressure of thehydraulic oil to the container cylinders 28, and is applied to thecontainer 18 in the extrusion direction through the container cylinders28.

Ideally, the complementary pressure Pa preferably has the absolute valuesame as the absolute value of the reduced container sealing force fd.Accordingly, as illustrated in FIG. 4C, the container sealing force f towhich the complementary pressure Pa is applied is coincident with thereference container sealing force fs even at timing when the extrusionmaterial EM has any extrusion material length L, during the period fromthe start to the completion of the extrusion. In other words, theextrusion press device 1 to which the complementary pressure Pa isapplied can maintain the reference container sealing force fs applied tothe container 18 in the extrusion direction at the start of theextrusion, during the period from the start to the completion of theextrusion. In the extrusion press method by the extrusion press device1, extrusion press at equal pressure is realized during the extrusionprocess in the above-described manner. Note that the container sealingforce f is coincident with the reference container sealing force fs asdescribed above; however, this occurs in an ideal situation, and thecontainer sealing force f and the reference container sealing force fsare not coincident with each other in a realistic apparatus.

[Equal-Pressure Extrusion Control Procedure]

The controller 85 continuously calculates the complementary pressure Paduring the period from the start to the completion of the extrusion. Thecontroller 85 controls the pressure control means 83 such that, in thecontrol hydraulic circuit 84, the hydraulic oil is supplied from thehydraulic-oil supply source 82 to each of the oil chambers (divided oilchamber 56B and divided oil chamber 66B) of each of the containercylinders 28 at the complementary pressure Pa calculated in real time.

Although the hydraulic-oil supply source 82 may be a variable dischargehydraulic pump, the hydraulic-oil supply source 82 is preferably ahydraulic pump that controls the discharge amount based on therotational speed of the driving motor. Further, as the pressure controlmeans 83, a pressure control device that can control the hydraulic oilpressure of the hydraulic circuit in real time, for example, aproportional solenoid relief valve is preferably adopted.

The extrusion press device 1 according to the first embodiment performsthe above-described equal-pressure extrusion control method, which makesit possible to maintain the container sealing force f at the referencecontainer sealing force fs (=Fb′max) during the period from the start tothe completion of the extrusion process as illustrated in FIG. 4C. Notethat, in FIG. 4C, the start of the extrusion process is specified byLmax, and the completion of the extrusion process is specified by Lmin.During the period, the reaction force Fb′ (in-extrusion containersealing force fex) is also reduced due to reduction of the extrudingforce F. However, the hydraulic oil of the complementary pressure Pamatching the reduction of the reaction force Fb′, namely, increase ofthe reduced container sealing force fb is supplied to the containercylinders 28. Therefore, it is possible to perform correction tocompensate the reduction of the reaction force Fb′. The correction isillustrated in a correction region A hatched in FIG. 4C. As a result ofthe correction, the extrusion press device 1 can maintain the containersealing force f substantially constant (at reference container sealingforce fs (=Fb′max)) during the extrusion process.

Further, in the above-described equal-pressure extrusion control method,the correction region A of FIG. 4C is increased and corrected bypressing the container 18 against the die 16 from the main cylinderhousing 12 side by the container cylinders 28 disposed in the maincylinder housing 12. As described above, the increasing amount of thereduced container sealing force fd is substantially equal to thereduction amount (Fbmax−Fb) of the frictional force Fb reduced duringthe extrusion process. The reaction force acting on the containercylinders 28 during the increase correction acts between the end platen10 and the main cylinder housing 12.

In other words, the force that acts on the same direction and issubstantially equal to the reduction amount of the extruding force Freduced during the extrusion process is increased and corrected by theabove-described equal-pressure extrusion control method. Accordingly,the force (reaction force of extruding force F) acting between the endplaten 10 and the main cylinder housing 12 during the extrusion processis also maintained at substantially constant. In other words, when thecorrection region A illustrated in FIG. 4C is increased and corrected,the extruding force F (Fa+Fbmax) is maintained during the period fromthe start to the completion of the extrusion process as illustrated byan alternate long and short dash line in FIG. 4B that illustratesvariation of the extruding force F during the extrusion process. Theextruding force F propagates to the end platen 10 through the die 16.

[Effects by First Embodiment]

Next, effects achieved by the extrusion press device 1 according to thefirst embodiment are described. The effects include an effect relatingto prevention of the bursting phenomenon and an effect relating toimprovement of dimension/shape accuracy of an extrusion molded product.Further, since the container cylinders 28 are adopted, the effectsinclude an effect to generate large output while preventing a cylinderdiameter from being increased.

[Effect Relating to Improvement of Dimension/Shape Accuracy]

According to the first embodiment, the complementary pressure Pacorresponding to the reduced container sealing force fd along withprogression of the extrusion is controlled to be applied to thecontainer 18 in the extrusion direction during the period from the startto the completion of the extrusion. As a result, the constant extrudingforce F propagating to the end platen 10 through the die 16 ismaintained during the period from the start to the completion of theextrusion. Accordingly, the amount of deflection occurred on the endplaten 10 and the die 16 caused by the extruding force F is maintainedin the state at the start of the extrusion, until the completion of theextrusion. Note that the deflection occurred on the end platen 10 isdeflection mainly caused by curved deformation, and the deflectionoccurred on the die 16 is deflection caused by compression in thelongitudinal direction X and curved deformation.

[Effect relating to Prevention of Bursting Phenomenon]

According to the first embodiment, the complementary pressure Pacompensating the reduced container sealing force fd along withprogression of the extrusion is controlled to be applied to thecontainer 18 in the extrusion direction during the period from the startto the completion of the extrusion. According to the first embodiment,applying the complementary pressure Pa makes it possible to secure thecontainer sealing force f sufficient to prevent the “burstingphenomenon” during the period from the start to the completion of theextrusion.

[Energy Efficiency]

Further, according to the first embodiment, since the reduced containersealing force fd is complemented by pressing in the extrusion direction,the extruding force F is not reduced. Thus, according to the firstembodiment, energy efficiency is improved as compared with the energyefficiency by Patent Literature 1 in which pressing is performed in thedirection opposite to the extrusion.

[Large Output is Possible While Preventing Cylinder Diameter fromIncreasing]

In the extrusion press device 1 according to the first embodiment, eachof the container cylinders 28 includes the plurality of, morespecifically, two oil chambers, the first oil chamber 51 and the secondoil chamber 61 along the longitudinal direction X. Further, the firstpiston 54 slidable in the longitudinal direction X in the first oilchamber 51 is formed on the first rod 52 communicating with the firstoil chamber 51, and the second piston 64 slidable in the longitudinaldirection X in the second oil chamber 61 is formed on the second rod 62communicating with the second oil chamber 61. As a result, the twodivided oil chambers 56A and 56B divided in the longitudinal direction Xby the first piston 54 are formed in the first oil chamber 51, and thetwo divided oil chambers 66A and 66B divided in the longitudinaldirection X by the second piston 64 are formed in the second oil chamber61. Accordingly, the container cylinders that can generate large outputare disposed in the main cylinder housing to obtain large containersealing force and large container split force while preventing thecylinder diameter from being increased. As a result, in the extrusionpress device 1 according to the first embodiment, the large containersealing force and the large container split force can be obtained.Further, supplying the hydraulic oil to one of the plurality of oilchambers makes it possible to drive each of the container cylinderswithout increasing the supply amount of the hydraulic oil.

Second Embodiment

Next, an extrusion press device 2 according to a second embodiment and amain-crosshead retreat control method by the extrusion press device 2are described with reference to FIG. 8.

The extrusion press device 2 itself according to the second embodimenthas the basic configuration same as the configuration of the extrusionpress device 1 according to the first embodiment, including theconfiguration of each of the container cylinders 28 disposed in the maincylinder housing 12. Accordingly, the components same as or notfunctionally different from the components illustrated in FIG. 1 andFIG. 5 are denoted by the same reference numerals as the referencenumerals in FIG. 1 and FIG. 5, and description of such components isomitted.

The extrusion press device 2 according to the second embodiment and theextrusion press device 1 according to the first embodiment are mainlydifferent in the hydraulic circuit. More specifically, the difference isthat the extrusion press device 2 includes a main-crosshead retreathydraulic circuit 284. The main-crosshead retreat hydraulic circuit 284can optionally select a communication state in which dischargedhydraulic oil discharged from the oil chambers (first oil chambers 51and second oil chambers 61) of the container cylinders 28 is supplied tothe side cylinders 26 and a closed state in which the dischargedhydraulic oil is not supplied to the side cylinders 26.

The discharged hydraulic oil is discharged when the container 18(container holder 19) is retreated by the container cylinders 28.Further, the discharged hydraulic oil is used to retreat the maincrosshead 22 by the side cylinders 26.

The extrusion press device 2 can perform the main-crosshead retreatcontrol method. The main-crosshead retreat control method reduces a timenecessary to retreat the container 18, the extrusion stem 24, and themain crosshead 22 for next extrusion process after completion of oneextrusion process by utilizing characteristics of the containercylinders 28. A procedure of the retreat control is described in orderbelow.

After the completion of the extrusion process, the container 18 and themain crosshead 22 (extrusion stem 24) are retreated to expose theextrusion material EM as a discard on an end surface of the die 16.

Next, an unillustrated shear device or the like to shear the discard islowered, from above, between the die 16 and the container 18, and thediscard exposed on the end surface of the die 16 is sheared and removed.

Next, the main crosshead 22 is retreated to a retreat limit position(main-crosshead retreating step), and preparation to store a newextrusion material EM in the container 18 is performed.

More specifically, a valve 201C is first closed to close the hydrauliccircuit that supplies the hydraulic oil from a main pump 282 (normally,provided in plural) as the main hydraulic-oil supply source to the sidecylinders 26. Thereafter, a valve 201E is opened to shift themain-crosshead retreat hydraulic circuit 284 from the closed state tothe communication state (container retreat preparation step).

Next, a space length to supply the new extrusion material EM is securedbetween the container 18 and the extrusion stem 24. To secure the spacelength, a valve 201A is opened to supply the hydraulic oil from the mainpump 282 to the divided oil chamber 56A (first oil chamber 51) and thedivided oil chamber 66A (second oil chamber 61) of each of the containercylinders 28, and the container 18 is retreated to the retreat limitposition (container retreating step). Note that, to increase theretreating speed of the container 18, the following procedure can beadopted. The hydraulic oil is supplied from the main pump 282 to one ofthe divided oil chamber 56A and the divided oil chamber 66A of each ofthe container cylinders 28, and the other divided oil chamber can suckthe hydraulic oil from a hydraulic oil tank through release of anunillustrated tank line.

At this time, the main-crosshead retreat hydraulic circuit 284 is in thecommunication state. Therefore, the hydraulic oil discharged from thetwo oil chambers of each of the container cylinders 28 is whollysupplied to oil chambers of the side cylinders 26 on the rod sidethrough the valve 201B. As a result, the main crosshead 22 is retreated.

Also in the existing extrusion press device, the discharged hydraulicoil discharged from the container cylinders 28 is wholly supplied to theside cylinders 26 to retreat the main crosshead 22 when the container 18is retreated, in some cases. However, the volume of the dischargedhydraulic oil discharged from the container cylinders 28 until thecontainer 18 reaches the retreat limit position is typically lower thanthe volume of the supplied hydraulic oil necessary to cause the maincrosshead 22 to reach the retreat limit position. In this case, afterthe container 18 has reached the retreat limit position, it is necessaryto switch the hydraulic circuit to supply the hydraulic oil from themain hydraulic-oil supply source to the side cylinders 26 and to retreatthe main crosshead 22 that has not reached the retreat limit positionyet, to the retreat limit position anew. This makes it difficult toreduce the time necessary to retreat the main crosshead 22 to theretreat limit position (main-crosshead retreating step).

As described in the first embodiment, the container cylinders 28 of theextrusion press device 2 can generate large output while preventing thecylinder diameter from being increased. This makes it possible toincrease the volume of the discharged hydraulic oil discharged from thecontainer cylinders 28. As a result, the main crosshead 22 is retreatedto a position closer to the retreat limit position before the container18 reaches the retreat limit position, which makes it possible to reducethe time necessary for the main-crosshead retreating step.

Further, the container cylinders 28 can be configured so as to make thevolume of the discharged hydraulic oil discharged from the containercylinders 28 themselves substantially equal to or larger than the volumeof the supplied hydraulic oil necessary to cause the main crosshead 22to reach the retreat limit position by the side cylinders 26. As aresult, the main-crosshead retreating step can be completed by theabove-described main-crosshead retreat control method at thesubstantially same time as or before completion of the containerretreating step. This makes it possible to further reduce the timenecessary for the main-crosshead retreating step. In addition, after thecompletion of the container retreating step, it is unnecessary to supplythe hydraulic oil from the main hydraulic-oil supply source to the sidecylinders for retreating operation of the main crosshead to the retreatlimit position again. As a result, it is possible to supply thesubstantially whole amount of hydraulic oil from the main hydraulic-oilsupply source to the shear device (discard shearing device), whichreduces the time necessary to shear the discard. As described above, itis possible to reduce not only the time necessary for the main-crossheadretreating step but also the idle time itself.

Further, the container cylinders 28 of the extrusion press device 2according to the second embodiment are disposed together with the sidecylinders 26 in the main cylinder housing 12. Accordingly, themain-crosshead retreat hydraulic circuit 284 can be configured with anextremely short hydraulic pipe length. This makes it possible to reduceassembly man-hours for the hydraulic pipes and the like of the extrusionpress device and to reduce the amount of hydraulic oil staying insidethe hydraulic pipes. Note that, since FIG. 8 is a schematic hydrauliccircuit diagram to perform the main-crosshead retreat control method bythe extrusion press device according to the second embodiment, only themain valves necessary for description have been denoted by the referencenumerals and described. Accordingly, all of the hydraulic devicesnecessary for the actual hydraulic circuit are not illustrated, andvalves not denoted by the reference numerals among the illustratedvalves are only illustrated as “opened” or “closed” in FIG. 8. Notethat, in the schematic hydraulic circuit diagram of FIG. 8, a symbol ofa variable discharge hydraulic pump is illustrated as the main pump 282;however, the main pump 282 may be a hydraulic pump, the discharge amountof which is controlled through rotational speed control of a drivingmotor.

Although the first embodiment and the second embodiment have beendescribed above as the preferred embodiments of the present invention,the present invention is not limited to the above-described embodiments,and can be implemented in various forms without departing from the scopedescribed in the appended claims.

For example, in the first embodiment, the reference container sealingforce fs and the in-extrusion container sealing force fex are detectedduring the extrusion process, and control to calculate the reducedcontainer sealing force fb, and the like are performed based on thedetection result; however, the present invention not limited thereto.The present invention includes, for example, the following forms.

In a case where extrusion press is repeatedly performed on the sameextrusion material by the extrusion unit having the same specificationunder the same extrusion condition, control is performed based on thereference container sealing force fs and the like detected during theextrusion process in the first extrusion press, in a manner similar tothe first embodiment. In a subsequent extrusion press, however,extrusion press with equal-pressure control can be performed by usingthe reference container sealing force fs and the like detected in thefirst extrusion press. More specifically, function data or table dataillustrated in the graph of FIG. 4C is generated in the first extrusionpress, and the equal-pressure control can be performed based on thegenerated data in the subsequent extrusion press.

Further, in the first embodiment, the tandem cylinder form in which eachof the container cylinders 28 includes the two oil chambers (first oilchamber 51 and second oil chamber 61) has been mainly described.Alternatively, as long as restriction of the arrangement of thecontainer cylinders in the main cylinder housing can be satisfied, aform including three or more oil chambers or a single cylinder form inwhich one oil chamber illustrated in FIG. 5 is divided by one piston maybe adopted.

Further, in the first embodiment, the control hydraulic circuit 84 hasbeen described on the premise of execution of the equal-pressureextrusion control method. In the present invention, however, thehydraulic oil supplied from the hydraulic-oil supply source 82 to thecontainer cylinders 28 may be selectively supplied to the divided oilchambers 56B and 66B or the divided oil chambers 56A and 66A of thecontainer cylinders 28 by a direction selector valve or the like. Toadvance the container 18, the former is selected. To retreat thecontainer 18, the divided oil chambers 56A and 66A are selected.

In the above-described case, as with the case in which the retreatingspeed of the container 18 is increased, the hydraulic oil is suppliedfrom the main pump 282 to only one of the divided oil chamber 56B (firstoil chamber 51) and the divided oil chamber 66B (second oil chamber 61)of each of the container cylinders 28. In contrast, the other dividedoil chamber may suck the hydraulic oil from a hydraulic oil tank throughrelease of an unillustrated tank line.

In the first embodiment, it has been described that the hydraulic-oilsupply source 82 can be driven together with the main hydraulic-oilsupply source at a time other than the extrusion process. Further, thehydraulic-oil supply source 82 may be driven together with the mainhydraulic-oil supply source not only in the case where the container 18is advanced but also in the case where the container 18 is retreated, bya method other than the equal-pressure extrusion control method.

For example, there are a case where the discard at the completion ofextrusion is long, a case where the extrusion material length L of theextrusion material EM inside the container 18 in the middle of theextrusion process is long due to extremely-small lot production, and acase where a high strength material is used. In these cases, thecontainer strip force that is force necessary to retreat the container18 is increased as compared with the normal container strip force. Whenthe large container strip force is necessary in such cases and a caseother than the cases, the hydraulic oil of pressure higher than thenormal pressure may be supplied to the container cylinders 28 by thepressure control means 83 to retreat the container 18. The configurationof each of the container cylinders 28 described in the first embodimentcan generate the high container strip force.

The equal-pressure extrusion control method has been described in thefirst embodiment, and the main-crosshead retreat control method has beendescribed in the second embodiment. To perform these control methods,the configurations described in the respective embodiments may becombined and included. In this case, both of the control method in thefirst embodiment and the control method in the second embodiment areperformable. For example, the valve 201B of the main-crosshead retreathydraulic circuit 284 in the main-crosshead retreat control methoddescribed in the second embodiment, is closed. When the main-crossheadretreat hydraulic circuit 284 is in the closed state in theabove-described manner, the equal-pressure extrusion control methoddescribed in the first embodiment is performable by the controlhydraulic circuit 84.

Furthermore, although the container cylinders 28 are disposed in themain cylinder housing 12 in the first embodiment and the secondembodiment, the container cylinders 28 may be disposed in an optionalobject as long as the container cylinders 28 can exert the function.

REFERENCE SIGNS LIST

-   1, 2 Extrusion press device-   3 Extrusion unit-   5 Control unit-   10 End platen-   12 Main cylinder housing-   12A Main cylinder-   12B Main ram-   14 Tie rod-   16 Die-   18 Container-   19 Container holder-   22 Main crosshead-   24 Extrusion stem-   26 Side cylinder-   28 Container cylinder-   28A Cylinder rod-   51 First oil chamber-   52 First rod-   53 First cylinder body-   54 First piston-   55 Seal fixing member-   56A, 56B, 66A, 66B Divided oil chamber-   61 Second oil chamber-   62 Second rod-   63 Second cylinder body-   64 Second piston-   65 Closing member-   71 Coupling portion-   81 Pressure detection means-   82 Equal-pressure extrusion control hydraulic-oil supply source-   83 Equal-pressure extrusion control pressure control means-   84 Equal-pressure extrusion control hydraulic circuit-   85 Controller-   201 valve-   201B Valve-   201C Valve-   282 Main pump-   284 Main-crosshead retreat hydraulic circuit-   A Correction region-   EM Extrusion material-   P1 Hydraulic pipe-   P2 Hydraulic pipe-   P3 Hydraulic pipe-   P4 Hydraulic pipe

1. An extrusion press device, comprising: an extruder comprising acontainer configured to store an extrusion material, and an end platenconfigured to support a die from which the extrusion material isextruded; and a controller configured to control operation of theextruder by controlling a container sealing force that presses thecontainer against the die, wherein the controller is configured tocontrol application of a complementary pressure corresponding to areduced container sealing force to the container in a direction of theextrusion during a period from a start to completion of the extrusion,the reduced container sealing force being increased during progressionof extrusion.
 2. The extrusion press device according to claim 1,wherein the controller is further configured to controls application ofthe complementary pressure such that a reference container sealing forceis maintained during the period from the start to the completion of theextrusion, the reference container sealing force being the containersealing force at the start of the extrusion.
 3. The extrusion pressdevice according to claim 2, wherein the controller is furtherconfigured to determine the container sealing force at the start of theextrusion as the reference container sealing force.
 4. The extrusionpress device according to claim 3, wherein the controller is furtherconfigured to determine the reduced container sealing force as adifference between the container sealing force during the extrusion andthe reference container sealing force.
 5. The extrusion press deviceaccording to claim 1, wherein the controller is further configured tocontrol application of the complementary pressure as a force of 20% ormore and 30% or less of a maximum actual extruding force at the start ofthe extrusion, to the container.
 6. The extrusion press device accordingto claim 1, wherein: the extruder comprises a container cylinderconfigured to advance the container toward the end platen or withdrawthe container from the end platen, the container cylinder comprises afirst oil chamber and a second oil chamber that are arranged in alongitudinal direction along the extrusion direction, and each of thefirst oil chamber and the second oil chamber comprises two divided oilchambers divided in the longitudinal direction.
 7. The extrusion pressdevice according to claim 6, further comprising: an equal-pressureextrusion control hydraulic circuit configured to supply hydraulic oilto one or both of the first oil chamber and the second oil chamber ofthe container cylinder when the container is advanced by the containercylinder, and the equal-pressure extrusion control hydraulic circuit isindependent of a hydraulic circuit configured to extrude the extrusionmaterial.
 8. An extrusion press method of extruding an extrusionmaterial from a die while pressing a container against the die with acontainer sealing force, the extrusion material being extruded from thedie and being stored in the container, the extrusion press methodcomprising; applying a complementary pressure corresponding to a reducedcontainer sealing force to the container in a direction of the extrusionduring a period from the start to completion of the extrusion, wherein:the container sealing force at a start of extrusion is a referencecontainer sealing force, the container sealing force during theextrusion is an in-extrusion container sealing force, and a differencebetween the reference container sealing force and the in-extrusioncontainer sealing force is the reduced container sealing force.
 9. Theextrusion press method according to claim 8, wherein the complementarypressure is applied such that the reference container sealing force ismaintained during the period from the start to the completion of theextrusion.
 10. The extrusion press method according to claim 8, wherein:the reference container sealing force and the in-extrusion containersealing force are based on information detected at and after the startof the extrusion, and the reduced container sealing force and thecomplementary pressure are determined during the extrusion, based on thedetected reference container sealing force and the detected in-extrusioncontainer sealing force.